code.delx.au - pulseaudio/blob - src/pulsecore/once-posix.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of PulseAudio.
   5
   6   Copyright 2006 Lennart Poettering
   7
   8   PulseAudio is free software; you can redistribute it and/or modify
   9   it under the terms of the GNU Lesser General Public License as published
  10   by the Free Software Foundation; either version 2 of the License,
  11   or (at your option) any later version.
  12
  13   PulseAudio is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with PulseAudio; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21   USA.
  22 ***/
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include <config.h>
  26 #endif
  27
  28 #include <pthread.h>
  29 #include <assert.h>
  30
  31 #include <pulsecore/mutex.h>
  32
  33 #include "once.h"
  34
  35 #define ASSERT_SUCCESS(x) do { \
  36     int _r = (x); \
  37     assert(_r == 0); \
  38 } while(0)
  39
  40 static pa_mutex *global_mutex;
  41 static pthread_once_t global_mutex_once = PTHREAD_ONCE_INIT;
  42
  43 static void global_mutex_once_func(void) {
  44     global_mutex = pa_mutex_new(0);
  45 }
  46
  47 void pa_once(pa_once_t *control, pa_once_func_t func) {
  48     assert(control);
  49     assert(func);
  50
  51     /* Create the global mutex */
  52     ASSERT_SUCCESS(pthread_once(&global_mutex_once, global_mutex_once_func));
  53
  54     /* Create the local mutex */
  55     pa_mutex_lock(global_mutex);
  56     if (!control->mutex)
  57         control->mutex = pa_mutex_new(1);
  58     pa_mutex_unlock(global_mutex);
  59
  60     /* Execute function */
  61     pa_mutex_lock(control->mutex);
  62     if (!control->once_value) {
  63         control->once_value = 1;
  64         func();
  65     }
  66     pa_mutex_unlock(control->mutex);
  67
  68     /* Caveat: We have to make sure that the once func has completed
  69      * before returning, even if the once func is not actually
  70      * executed by us. Hence the awkward locking. */
  71 }